Marriage and walis.....

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Can anyone help me out please? I'm confused.

I've been reading up on nikahs (sufi ones, if it makes a difference?) etc. As a Christian possibly marrying a Muslim guy, would I need a wali? As I only have my 13 year old (atheist) son, I don't have anyone. What would have to happen please? Would I have to say anything in Arabic too? Hope someone can help. Thank you xx